This invention relates to syringes, particularly although not exclusively for dental use, and is more particularly concerned with safe disposal of needles of such syringes.
A conventional dental syringe has a barrel with a plunger mechanism at a rear end and a threaded adaptor to receive a needle at a front end. In use a glass cartridge, which contains an injectable liquid between a rear bung and a front membrane, is inserted into the barrel. A needle having a threaded hub adjacent to its rear end is screwed onto the adaptor so that it penetrates the cartridge membrane, and the plunger mechanism is engaged with the bung at the rear end of the cartridge.
After use, the cartridge and needle are removed and discarded. For safety purposes, the needle may be deposited in a so-called ‘sharps’ container for safe disposal.
In order to avoid needle-stick injuries there have been various proposals for facilitating safe handling of the needle during removal and disposal.
EP 0441628A describes the use of a removal device, which may be power operated, to unscrew the needle for deposit in a sharps container without requiring direct manual contact with the needle hub or syringe adaptor. However, there is the problem of avoiding contact with the needle after use and prior to its presentation to the removal device.
U.S. Pat. No. 5,403,288 and U.S. Pat. No. 5,989,226 describe the use of a sleeve which can be fitted over the needle after use. This arrangement can give effective protection against needle stick injuries. However, there is then the problem of convenient removal and disposal of the covered needle. In each case the needle is removed together with the sleeve which is in practice requires the sleeve and possibly associated components or even the entire syringe to be disposable. Whilst disposable syringes can be acceptable there is also a requirement for syringes which have re-usable main parts.
One object of the present invention is to enable the needle of a syringe to be easily and conveniently removed for disposal whilst being effectively protected within a sleeve to prevent needle-stick injuries but without requiring disposal of the sleeve with the needle.
According to one aspect of the invention therefore there is provided a method for disposal into a container of a needle mounted on a syringe via a push-fit mounting device,                the syringe having a barrel to receive a cartridge of injectable liquid with a forward end on to which the mounting device is a push-fit, a plunger mechanism connected to a rearward end of the barrel, and a sleeve mounted relative to the barrel so as to be slidable forwards to a position at which it sheaths the needle,        the container having a disposal chamber with an opening thereto provided with a receiving structure having a gripper device,        wherein the syringe is presented to the said receiving structure with the needle sheathed by the said sleeve, the sleeve is pushed back to expose the needle, and the mounting device passes beyond the said gripper device,        and the syringe is then withdrawn so that the needle with the mounting device is pulled off the syringe barrel, for deposit in the disposal chamber, by engagement of the mounting device with the gripper device.        
With this method the needle can be protected by the sleeve as it is presented to the container opening and the needle can then be removed and deposited in the container without requiring disposal of the sleeve. The needle can therefore be removed and safely discarded easily and conveniently, and the main parts of the syringe, including the sleeve, can then be re-used with a fresh needle and mounting device.
Preferably, the arrangement is such that the gripper device is a non-return device which engages behind the mounting device so as to abut a rear structure, such as a rear end edge or face, of the mounting device. Most conveniently the gripper device may be arranged to extend peripherally or circumferentially around relative to the syringe axis and thus, for example may comprise a ring of gripper fingers which are preferably resiliently deflectable to allow passage of the mounting device therethrough.
In order to ensure that the mounting device passes beyond the gripper device sufficiently to ensure that it is pulled off when the syringe is withdrawn, indicator marks or the like may be provided e.g. on the receiving structure and the syringe sleeve for alignment purposes, and/or the gripping device may be visible.
Preferably also, the arrangement may be such that the receiving structure engages a part, particularly a rear part, of the sheath, such as an enlarged rear collar, so as to push back the sheath.
In a particularly preferred embodiment the sleeve can be retained in the said forwards position by a releasable locking device, whereby this device is released after presentation of the syringe to the container opening has commenced.
The mounting device may comprise a unitary member attached, particularly permanently attached, to or integrated with the needle, as a so-called needle hub.
Alternatively the mounting device may comprise a combination of two parts comprising a needle hub integrated with the needle, and an adaptor which is a push-fit on the forward end of the barrel and to which the needle hub is connected.
Thus and in accordance with a second aspect of the invention there is provided a syringe, for use with the above method, comprising a barrel to receive a cartridge of injectable liquid, said barrel having a forward end for connection to a needle having a mounting hub, and a rearward end for connection to a plunger mechanism, a needle adaptor for mounting on the forward end of the barrel for retaining engagement with a hub of the needle to form with said hub a mounting device for the needle, and a sleeve mounted relative to the barrel so as to be slidable forwards to a position at which it is retained on the barrel but extends beyond the forward end to sheath the needle, characterised in that the needle adaptor is a push-fit on the forward end of the barrel whereby the needle and adaptor can be separated from the barrel and the sleeve by application of a linear acting removal force to the said adapter.
This arrangement allows the needle to be removed and discarded separately from the sleeve.
Also, insofar as removal requires only the application of a linear pull-off force, the needle can be detached in a particularly quick and convenient manner notwithstanding the presence of the sleeve.
With regard to the push-fit adaptor, this may be in the form of an end piece comprising a cap with one or more internal configurations such as projections which interengage surfaces or cooperable configurations of the barrel to establish a retaining e.g. tight frictional and/or snap fit.
The interengagement between the needle hub and the end-piece may be effected, in conventional manner, by screw fit engagement of an internal thread of the hub and an external threaded projecting part of the cap.
With regard to the receiving structure of the container of the above described method, this preferably comprises a passageway with an outer end through which the syringe is presented to the said opening, an inner end in communication with the said opening and having the gripper device thereat, and an abutment structure, e.g. at the outer end, for engagement with the sleeve to push this back.
Thus, and in accordance with a third aspect of the present invention there is provided a container for use with the above mentioned method comprising a disposal chamber having an opening thereto, and a receiving structure with a gripper device for holding a mounting device of a syringe needle to cause the needle to be pulled off the syringe on withdrawal thereof from the gripper device, characterised in that the receiving device comprises a passageway with an outer end through which the syringe is presented to the said opening and an inner end in communication with the said opening and having the gripper device thereat.
The gripper arrangement may be a non-return gripper which cooperates with a trailing abutment of the mounting device and thus may comprise a collar or ring having inwardly directed fingers which may deflect outwardly to allow passage of the abutment and then return inwardly to catch behind the abutment. This trailing abutment may comprise a rear end face or rim of the mounting device.
Other gripper arrangements of the nature of catch or interlock or abutment devices may also be used.
With regard to the passageway, most preferably the arrangement is such that this will receive the syringe barrel and the needle, but will not allow complete passage of the syringe sleeve whereby this is retracted as the syringe is inserted. Thus, the passageway preferably has an abutment structure arranged to engage a part e.g. an enlarged rearward end portion of the syringe sleeve. This abutment structure may be defined e.g. by a shoulder or rim at an entrance to the passageway.
The passageway may comprise a tube, such as a cylindrical tube.
The chamber may be a box capable of receiving multiple needle/mounting device combinations for disposal. Thus the chamber may be of substantially greater volume than the aforesaid passageway. This chamber may be linked to the passageway transversely to the direction in which the needle is inserted through the opening.
Alternatively to a multi-use box, the chamber may be for single use. In this case it may be of the nature of a tube with the opening through which the needle is inserted having an entrance at one end. The gripper device may also act, or be used in combination with, a holding device so that after detachment the needle/mounting device combination is held in position in the container. In this case, the tube may be open at the end remote from the needle entrance.
The sleeve of the syringe used with the above mentioned method may be mounted on the barrel so as to be slidable between rear and forward positions at which respectively the needle is arranged to be fully exposed and fully covered. At these limit positions the sleeve may be held in position frictionally and/or by a releasable catch or the like.
In one embodiment, the syringe sleeve has mounted thereon a member movable between release and locking positions whereby in the locking position cooperable configurations on the member and on the barrel interengage to prevent relative longitudinal movement of the member and the barrel and in the release position these configurations are disengaged to permit longitudinal movement.
Thus and in accordance with a further aspect of the invention there is provided a syringe for use with the above described method comprising a barrel to receive a cartridge of injectable liquid, said barrel having a forward end for connection to a needle via a push-fit mounting device, and a rearward end for connection to a plunger mechanism, and a sleeve mounted relative to the barrel so as to be slidable forwards to a position at which it is retained on the barrel but extends beyond the forward end to sheath the needle, characterised in that the syringe sleeve has mounted thereon a member movable between release and locking positions whereby in the locking position cooperable configurations on the member and on the barrel interengage to prevent relative longitudinal movement of the member and the barrel and in the release position these configurations are disengaged to permit longitudinal movement.
Preferably the movable member is provided at the rear end of the sleeve.
Conveniently, the movable member is rotatable about the axis of the barrel between locking and release positions. These positions may be limit positions which may be defined by interengagement of a peg with a slot, or by aligned markers or otherwise. The cooperable configurations may comprise a projection, particularly an elongate projection, on the member and a slot or groove in a projecting part of the barrel or vice versa.
The syringe sleeve may have a main tubular body part restrained against rotation around the barrel i.e. so that it is guided for longitudinal movement along the barrel. This may be achieved by means of a longitudinal groove or slot on one and a projection, particularly an elongate projection, which engages the groove or slot on the other and these may be aligned with the aforesaid projection and slot or groove of the movable member in the release position thereof.
The rotatable member may also comprise a tubular part or collar which is preferably of shorter length than the aforesaid main body part.
The syringe of this further aspect of the invention may have any or all of the features of the syringe of the second aspect of the invention.